Method to determine operating conditions of wavelength tunable laser diode and to control optical transmitter providing wavelength tunable laser diode
AssigneeSumitomo Electric Industries, Ltd.
InventorTsutomu ISHIKAWA
Life of this patent
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Abstract
A method to control a wavelength tunable laser diode (tunable LD) is disclosed. The tunable LD includes a SG-DFB region and a CSG-DBR region to tune the emission wavelength thereof. The CSG-DBR region includes three segments, where the refractive indices of respective segments are variable by heaters provided therein. When the electrical power supplied to two segments is optionally selected, the power supplied to the rest segment is corrected by an offset from a value reflecting physical dimensions of the heaters. The offset is determined such that the tunable LD shows the best side mode suppression ratio (SMSR).
Claims13
A method to tune an emission wavelength of a wavelength tunable laser diode (tunable LD) that provides a chirped sampled grating diffraction Bragg reflector (CSG-DBR) region to tune the emission wavelength of the LD, the CSG-DBR region having at least three segments each formed by a diffraction grating and a space, the space having no diffraction grating and being next to the diffraction grating, the segments having respective optical lengths, L1 to L3, and heaters, the respective optical lengths, L1 to L3 satisfying a relation of L1=L3+(L2−L3)×K (0.3<=K<=0.7), the method includes a step of supplying power, P1 to P3, to respective heaters, the power satisfying a relation of:
- P1=P3·Rth3/Rth1+(P2·Rth2/Rth1−P3·Rth3/Rth1)×K+Poffset,
- where Rth1 to Rth3 are thermal resistance of respective heaters, and Poffset is optimum offset power.
A method to tune an emission wavelength of a wavelength tunable laser diode (tunable LD) that provides a chirped sampled grating diffraction Bragg reflector (CSG-DBR) region to tune the emission wavelength of the tunable LD, the CSG-DBR region having at least three segments each formed by a diffraction grating and a space, the space having no diffraction grating and being next to the diffraction grating, the segments having respective optical lengths, L1 to L3, and heaters, the respective optical lengths, L1 to L3 satisfying a relation of L1=L3+(L2−L3)×K (0.3<=K<=0.7), the method includes a step of supplying power, P1 to P3, to respective heaters, the power satisfying a relation of:
- P1=P3·Rth3/Rth1+(P2·Rth2/Rth1−P3·Rth3/Rth1)×K+(1+Kopt),
- where Rth1 to Rth3 are thermal resistance of respective heaters, and Kopt is an optimum correction factor.
A method to control an optical transmitter that provides a wavelength tunable laser diode (tunable LD), a controller, and a memory look-up-table (LUT), the tunable LD integrally having a sampled grating distributed feedback (SG-DFB) region and a chirped sampled grating distributed Bragg reflector (CSG-DBR) region including at least three segments each having a diffraction grating and a space neighbor to the diffraction grating, each of segments having a heater and an optical length satisfying a relation of:
- L1=L3+(L3−L2)·K,
- where L1 to L3 are respective optical lengths and K is a constant of 0.3<=K<=0.7, the method comprising steps of:
- evaluating parameters to define an emission wavelength of the tunable LD, the parameters including currents supplied to respective heaters, optimum offset power supplied to the heater in the first segment, and an operating temperature of the tunable LD;
- storing the parameters to the memory LUT;
- and
- practically operating the tunable LD by performing steps of,
- receiving a target emission wavelength at which the tunable LD emit laser light,
- reading parameters corresponding to the target emission wavelength from the memory LUT, and
- controlling respective elements based on the parameters,
- wherein the step of evaluating the parameters includes steps of,
- varying power, P1 to P3, supplied to respective heaters based a relation of,
- P1=P3·Rth3/Rth1+(P2·Rth2/Rth1−P3·Rth3/Rth1)+offset,
- where Rth1 to Rth3 are thermal resistance of respective heaters and offset is offset power supplied to the heater in the first segment;
- measuring an emission wavelength and a side mode suppression ratio (SMSR) at the emission wavelength for the offset power;
- evaluating a wavelength tunable range of the tunable LD, where the wavelength tunable range is a range the SMSR exceeds a preset value;
- iterating the steps of varying power, measuring the emission wavelength and the SMSR, and the evaluating the wavelength tunable range as varying the offset;
- determining the optimum offset power at which the wavelength tunable range becomes a maximum.
Dependencies are inferred from the claim text.